Gazelle/image.php

<?php
declare(strict_types=1);

// Functions and headers needed by the image proxy
error_reporting(E_COMPILE_ERROR|E_RECOVERABLE_ERROR|E_ERROR|E_CORE_ERROR);

if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
    header('HTTP/1.1 304 Not Modified');
    error();
}

header('Expires: '.date('D, d-M-Y H:i:s \U\T\C', time() + 3600 * 24 * 120)); // 120 days
header('Last-Modified: '.date('D, d-M-Y H:i:s \U\T\C', time()));

if (!extension_loaded('gd')) {
    error('nogd');
}

function img_error($Type)
{
    header('Content-type: image/gif');
    error(file_get_contents(SERVER_ROOT.'/sections/image/err_imgs/'.$Type.'.png'));
}

function invisible($Image)
{
    $Count = imagecolorstotal($Image);
    if ($Count === 0) {
        return false;
    }
    $TotalAlpha = 0;
    for ($i = 0; $i < $Count; ++$i) {
        $Color = imagecolorsforindex($Image, $i);
        $TotalAlpha += $Color['alpha'];
    }
    return (($TotalAlpha / $Count) === 127);
}

function verysmall($Image)
{
    return ((imagesx($Image) * imagesy($Image)) < 25);
}

function image_type($Data)
{
    if (!strncmp($Data, 'GIF', 3)) {
        return 'gif';
    }
    if (!strncmp($Data, pack('H*', '89504E47'), 4)) {
        return 'png';
    }
    if (!strncmp($Data, pack('H*', 'FFD8'), 2)) {
        return 'jpeg';
    }
    if (!strncmp($Data, 'BM', 2)) {
        return 'bmp';
    }
    if (!strncmp($Data, 'II', 2) || !strncmp($Data, 'MM', 2)) {
        return 'tiff';
    }
    if (!substr_compare($Data, 'webm', 31, 4)) {
        return 'webm';
    }
}

function image_height($Type, $Data)
{
    $Length = strlen($Data);
    global $URL, $_GET;

    switch ($Type) {
    case 'jpeg':
      // See http://www.obrador.com/essentialjpeg/headerinfo.htm
      $i = 4;
      $Data = (substr($Data, $i));
      $Block = unpack('nLength', $Data);
      $Data = substr($Data, $Block['Length']);
      $i += $Block['Length'];
      $Str []= 'Started 4, + '.$Block['Length'];

      while ($Data !== '') { // Iterate through the blocks until we find the start of frame marker (FFC0)
        $Block = unpack('CBlock/CType/nLength', $Data); // Get info about the block
        if ($Block['Block'] !== '255') { // We should be at the start of a new block
          break;
        }

          if ($Block['Type'] !== '192') { // C0
          $Data = substr($Data, $Block['Length'] + 2); // Next block
          $Str []= 'Started $i, + '.($Block['Length'] + 2);
              $i += ($Block['Length'] + 2);
          } else { // We're at the FFC0 block
          $Data = substr($Data, 5); // Skip FF C0 Length(2) precision(1)
          $i += 5;
              $Height = unpack('nHeight', $Data);
              return $Height['Height'];
          }
      }
      break;

    case 'gif':
      $Data = substr($Data, 8);
      $Height = unpack('vHeight', $Data);
      return $Height['Height'];

    case 'png':
      $Data = substr($Data, 20);
      $Height = unpack('NHeight', $Data);
      return $Height['Height'];
      
    default:
      return 0;
  }
}

define('SKIP_NO_CACHE_HEADERS', 1);
require_once 'classes/script_start.php'; // script_start.php contains all we need and includes sections/image/index.php